This invention relates generally to an apparatus and a method for reclaiming waste oil, more particularly for removing various contaminants present in waste oil which make it unsuitable for re-use as a heating fuel, diesel fuel, and so forth.
In this specification, the term xe2x80x9cwaste oilxe2x80x9d encompasses any suitable oil, for example, mineral oil, which has been used as motor oil or some other lubricating oil, or as hydraulic oil or in some other such application. It is anticipated that these oils will have be en derived from mineral oil, but they could be, for example, animal or vegetable oil, i.e. such as fish oil or oil discarded by restaurants, etc. The mineral oil could be plain crude oil. In use, such lubricating oils are changed periodically. The drained and recovered waste oil typically contains substantial amounts of contaminants, which may include dirt, metallic particles (including heavy metals, such as molybdenum, chromium, vanadium, copper and so forth), oxides and salts, gasoline and gasoline additives (such as tetraethyl lead), as well as detergents and performance additives. It may also include water. The contaminants in crude oil usually make it unsuitable for most uses.
Many millions of gallons of such waste oil are produced annually in North America. In the past, waste oil has been used on dirt roads for dust control, or simply dumped in sanitary sewers or land fill sites. However, increasingly such methods of disposal are seen as being unacceptable causes of hydrocarbon pollution to the environment. Re-refining of waste oil is practised to a certain extent. However, known methods for re-refining waste oil require complex chemical treatments and generally do not produce a high grade product. Transportation costs further detract from the economic viability of this manner of dealing with waste oil.
In the past, it has also been proposed that waste oil be used as a heating fuel. However, furnaces of the known type for burning such oil have met with limited success. During conventional combustion of waste oil, a residue accumulates in the burner. The residue is formed of the various contaminants and the heavier hydrocarbon which form a hard binding resin. As a result, the burner must frequently be cleaned of the accumulated hard residue, typically twice per day. In order to clean the burner, the furnace must be turned off and allowed to cool. This is extremely inconvenient and represents major inefficiency. Furthermore, removal of the cooled and hardened residue from the burner is a difficult task typically requiring strenuous physical labour.
xe2x80x9cIn accordance with the present invention, there is provided a method for treating waste oil containing contaminants, the method comprising the steps of:
(a) heating said waste oil;
(b) at substantially atmospheric pressure, volatilizing a first portion of said waste oil, at a temperature sufficient to cause cracking of at least part of said first portion, said first portion containing primarily the lighter hydrocarbons of said waste oil, and separating the volatilized first portion from the remaining unvolatilized portion of said waste oil, said remaining portion containing primarily the heavier hydrocarbons and the contaminants of said waste oil;
(c) condensing said separated, volatilised first portion; and
(d) recovering said condensed first portion, substantially reduced in contaminants and having a substantially lower viscosity than said waste oil, and separately recovering said remaining portion. Preferably, the temperature is in the range of from about 600 to 800xc2x0 F. Advantageously, the temperature is about 650xc2x0 F. Most advantageously, the volatilized lighter hydrocarbons are subsequently condensed to produce a reclaimed liquid oil product, at. least a portion of which is then burned to heat more waste oil in the boiler.
The present invention provides a safe, efficient and versatile means for treating waste oil, reclaiming therefrom a useful petroleum product which can be used in a number of ways, particularly as a heating fuel or as diesel fuel. The sludge by-product derived from the heavier hydrocarbons and contaminants must still be disposed of. However, it should typically represent approximately only one-tenth of the volume of the waste oil fed to the apparatus. In some cases it may be possible to reclaim valuable metals from the sludge product.
An apparatus for carrying out the present invention can be manufactured and operated at a small fraction of the cost of a re-refining plant. Thus, industrial and commercial establishments (such as automobile service stations) and others who accumulate large quantities of waste oil can utilize the waste oil as a valuable by-product, rather than having to pay to have it disposed.